So my car has been a very reliable and fun daily driver and weekend track car...to the point I would say it one of the best platforms for a DD/Weekend Warrior.

This next year will be much more focused on Track events and less on daily driveability...I'm registered for NASA TT-A (unfortunately the fastest class..Ill likely get less-grippy tires to shed some points) and will be doing quite a bit more competitive events..(Red Line TT, Super Lap Battle, etc)

The car is a 2008 E90 335i...on the street it has 440hp/500tq; however due to heat and snail-sized snails, it is capped to 300/300 for the track. (which also keeps points/class down) Suspension is fully setup with ASTs, good control arms, alignment, etc. The main things that are seperating this car from being a full-on track car is 1) Full-on Role Cage/completely gutting the interior and 2) Complete Aero system.

Since it is still a DD and I don't intend on it being a dedicted track car, I'm not concerned about a roll cage at this point.
So that leaves the Aero system. I’ve done a LOT of extreme-learning over the past month or so and have a complete new understanding of the complexity of aerodynamics when applied to cars; sedans in particular.

In short, the goal with any track car is to:
1) Reduce drag… including making the front as concise and smooth as possible, limiting the amount of air that is allowed under the car, making the body streamlined, and reducing the Flow Separation/rear vacuum created by the car’s wake.

2) Increase Downforce…this is the fun part. Most of the downforce will be created by low pressure underneath side of the car; with the fine tuning of wings, Canards and air dams.
The underbody should be made up of 4 Pieces: Splitter, Undertray, Side Skirts and Rear Diffuser. The most important thing to keep in mind with all of this; is that everything works as a system. None of these pieces alone will achieve high results unless they are all in place and functioning properly.

Splitter- There are 2 benefits of the front splitter.
1) To split air. Duh. This is the lowest, level piece of the front of the car; the choke point for the air to get underneath. This reduction of air is noticed throughout the entire underbody. Not only does it simply reduce it…but because of the smooth undertray it is accelerated. According to Bernoulli’s Principle, Accelerated air = lower pressure. Lower Pressure beneath = downforce. The lower it goes; the better the car blows

2) To provide real-estate for the high-pressure air that is created by the front bumper pushing through the air. The airdam (piece right above the splitter) essentially blocks the air; and the high pressure pushes down on the splitter. splitter3 by MDM Enterprises, on Flickr

Underbody Smoovness- This is pretty self- explanatory. Many cars today come with semi-smooth belly pans; but anything rear of the transmission is bare and bumpy. Any open areas, exhaust channels, subframes/control arms, etc. create turbulence. This turbulence slows down the air, creates drag and minimizes the effect of the system.
**It is important to note that the underside of the car does serve another purpose: To extract heat from the engine bay. There is very high pressure in the engine bay from the incoming air; and it can only go through the gap between the hood and windshield (also high pressure), or flow backwards around the transmission and out an opening in the underbody. Because of this I’ve left open the area behind the transmission and front of the exhaust tunnel. The extra low pressure of this whole system should also help extract more heat. underbody3 by MDM Enterprises, on Flickrunderbody2 by MDM Enterprises, on Flickr

Diffuser- This puts the “rice” in “Hey, look at that ricer”. Whilst it may end up looking like KTran’s NSX, the gains to be had from it are incredible. The basic goals of a diffuser are to utilize the expanding area to slow down the air whilst not increasing pressure, so that when the faster air under the car meets the slower air on top of the car, less Flow Seperation (Vacuum bubble) occurs…which reduces drag.
The angle of attack for the diffuser should be adjustable from 6-15*; with 9.5* being seen as “ideal”. Thankfully my design just happened to be adjustable in that exact range
The design of my diffuser was VERY much controlled by the exhaust muffler and tips hanging down. For practicality’s sake, It would have been ideal to have the rear diffuser flat across,and span the width of the inside of the entire car, and be fenced off inside of the rear wheels. If it weren’t for the large muffler; I’d be able to use a better starting height and slow down the air even more. So this forced me to do a 3-piece design, which has two static sides (behind the rear wheels) and one center section under the muffler which is adjustable.

Side Skirts/Fences. Now if the splitter, diffuser and complete underbody were setup, then that would create very low pressure underneath the car. …however that low pressure would instantly be balanced by the atmospheric pressure outside of the underbody… eliminating any real benefit of this aero system. Because of this, it is important to “fence” off the underbody so that the low pressure stays inside where it belongs.

To test this I’ve bought a Digital Manometer; which can measure very small pressure differentials between two areas. Extrapolating data into the entire system will be difficult; but I simply want to see a significant pressure decrease and also use it to troubleshoot other problem areas.

All in all; I am hoping this aero system will convert the ~150lbs lift into 500lbs of downforce at 100mph. I will definitely update this as I collect data and have some experiences on the track!
Thanks for reading,
Brian

Awesome work! Love it. Did you remove the OE front undertray or does this mount onto that? Also, what is this made of? When the front hits something, is it cheap to repair or replace?

Thanks! For now the rear of section of the front undertray is retained; as the splitter can only be 4 feet long (they don't make ABS sheets larger than that). Eventually ALL of these parts will be molded/vacuformed and made with carbonfiber. Then itll be possible to make them any size.

Even with many parts being carbon, I'll likely keep the front splitter 3/8" ABS Plastic as it is rigid, yet flexible and cheap. (It is only 1/8" plastic now; so it needs to get a bit thicker and protrude out farther for the actual track use)

Quote:

Originally Posted by jbass524

A Vorsteiner vented hood? I feel this should really be in your plan to help extract heat from the engine bay assuming you're running hot.

That is definitely on my wish list at the moment. A vented hood will definitely help with heat, and reduce some drag at the same time. Doing that will also allow me to seal off the hood-windsheild gap; further improving aero. And yes, I'm running very hot...oil temps easily being 280* w/o meth....even with the AR Oil cooler. With meth Oil temp stays around 265ish.

That is definitely on my wish list at the moment. A vented hood will definitely help with heat, and reduce some drag at the same time. Doing that will also allow me to seal off the hood-windsheild gap; further improving aero. And yes, I'm running very hot...oil temps easily being 280* w/o meth....even with the AR Oil cooler. With meth Oil temp stays around 265ish.

Brian

Take it from someone who has had one, the AR cooler is almost useless. If you haven't read the sticky on Limp mode party at the track you should.

Here's the solution anyone tracking as much as you should have:

Evolution Racewerks Competition or Stett dual oil coolers

Aftermarket radiator w/higher capacity if you can find one

Distilled water with MOCOOL

You already have the other stuff.

Our cars suffer from horrid cooling and the coolant water is ignored when it should be a focus. That's why the distilled water and a big radiator if you can find one.

Take it from someone who has had one, the AR cooler is almost useless. If you haven't read the sticky on Limp mode party at the track you should.

Here's the solution anyone tracking as much as you should have:

Evolution Racewerks Competition or Stett dual oil coolers

Aftermarket radiator w/higher capacity if you can find one

Distilled water with MOCOOL

You already have the other stuff.

Our cars suffer from horrid cooling and the coolant water is ignored when it should be a focus. That's why the distilled water and a big radiator if you can find one.

The hood will help too.

Thanks. I have been eyeing up the ER dual core setup for a while too; and actually saw it for the first time about a week after I got the first AR Oil cooler.

I'll likely swap out the OEM oil cooler for a better core and see how that goes.

I've already got pure distilled with RL's Water Wetter in the radiator; and wouldn't hesitate to buy an aftermarket aluminum radiator...if there was one and it was under $1k. AR had made one, but I don't think they plan on producing it anymore.

Thanks. I have been eyeing up the ER dual core setup for a while too; and actually saw it for the first time about a week after I got the first AR Oil cooler.

I'll likely swap out the OEM oil cooler for a better core and see how that goes.

I've already got pure distilled with RL's Water Wetter in the radiator; and wouldn't hesitate to buy an aftermarket aluminum radiator...if there was one and it was under $1k. AR had made one, but I don't think they plan on producing it anymore.

I went through all of this and I highly suggest just losing the AR OC. Really. It blocks precious radiator area and isn't big enough to do what our cars need. It's also not fully exposed. The ER solution has ducting specifically designed for it for maximum air flow and you get all of your radiator back.

I went through all of this and I highly suggest just losing the AR OC. Really. It blocks precious radiator area and isn't big enough to do what our cars need. It's also not fully exposed. The ER solution has ducting specifically designed for it for maximum air flow and you get all of your radiator back.

No more hijacking your aero thread. Apologies.

Haha no worries; this is the exact stuff I like to discuss.

I do agree the ER is ideal; just trying to see what I can do before shelling out the ca$h for it. In my opinion the area blocking the radiator is not large enough/blocking enough to make it noticeable. Air still flows through it just fine; and at speed that is a lot of cold air.

I do agree the ER is ideal; just trying to see what I can do before shelling out the ca$h for it. In my opinion the area blocking the radiator is not large enough/blocking enough to make it noticeable. Air still flows through it just fine; and at speed that is a lot of cold air.

You gotta trust me. I made the mistakes and so have others - orionredwing for one. Not enough air to the radiator. Don't discount how important coolant/water temps are alleviating heat soak as much as possible is. To qualify, with stock power I have gone 1:47 at Laguna, 1:57 Infineon, 2:06 Thunderhill (w/bypass). Not great but I do drive hard.

You gotta trust me. I made the mistakes and so have others - orionredwing for one. Not enough air to the radiator. Don't discount how important coolant/water temps are alleviating heat soak as much as possible is. To qualify, with stock power I have gone 1:47 at Laguna, 1:57 Infineon, 2:06 Thunderhill (w/bypass). Not great but I do drive hard.

The strange thing is though- Water temps are usually in check...right around 195-205*F. The water temp did not go up AT ALL with the addidition of the Oil cooler..same track, same ambient temp...that absolutely leads me to believe that the oil cooler does not effect or impede water temps.

Do you have data that shows otherwise?

Hope I'm not coming off as argumentative...just trying to advance the topic

I don't have data other than limping due to oil temps with the AR and it wasn't a fuel pump, turbo or anything else that caused the limps, session after session. Ambient was under 70 at Laguna and I couldn't get more than 5 laps in. That's less than 10 minutes of driving.

We have also deduced that the water temps suffer as much as oil temps in our cars and the AR inhibits that cooling while only being marginally effective as an additional oil cooler. You can find a thread on checking temps and it's in the limp mode party sticky.

The other potential is that because ambient temps in MN are low and you're not driving as hard as you could the car never gets that hot. We have found that many that don't have a problem aren't going that fast. How do your times compare with the pro Miata drivers...seriously. Just trying to help and be deductive.

For this discussion you should take it to the limp mode sticky. It's been covered in great detail over and over.

I don't have data other than limping due to oil temps with the AR and it wasn't a fuel pump, turbo or anything else that caused the limps, session after session. Ambient was under 70 at Laguna and I couldn't get more than 5 laps in. That's less than 10 minutes of driving.

We have also deduced that the water temps suffer as much as oil temps in our cars and the AR inhibits that cooling while only being marginally effective as an additional oil cooler. You can find a thread on checking temps and it's in the limp mode party sticky.

The other potential is that because ambient temps in MN are low and you're not driving as hard as you could the car never gets that hot. We have found that many that don't have a problem aren't going that fast. How do your times compare with the pro Miata drivers...seriously. Just trying to help and be deductive.

For this discussion you should take it to the limp mode sticky. It's been covered in great detail over and over.

Haha, almost all of the track days last year were in the 80s or 90s. And yes, the car was absolutely getting pushed hard. For comparisons' sake; I can pull consistent RA Lap times in the high 2:20s at Road America...Spec miatas are around 2:45. Not to sound like a D-Bag; but I'm able to dice with GT3s with very accomplished Porsche Club of America instructors and former ALMS drivers; and consistently 8-15 seconds faster than most of the other non-track prepped E46 and E90 M3s. So suffice it to say I doubt it is possible to push the car harder than I am. I realize that sounds like a total bro thing to say; but it's the facts.

That said, my results simply show different than yours. My water temps are never higher than 210, and that water temp was unaffected by the addition of the AR Oil Cooler. I realize that theory would suggest that the water temps would go up; but the fact is that the radiator isn't "blocked", rather the air is simply slowed down and heated up a little prior to going through the radiator in the area the oil cooler is.

After upgrading the OEM oil cooler, (assuming I see no major difference in Oil Temps), I'll undoubtedly place a second core in the drivers side wheel well.

Ideally the goal I'd like to get to is 250*. As mentioned, meth has brought temps down from 285 to 265...so I guess I simply don't know what to expect with the additional oil cooling at the moment.

Regarding your limps: I assume you were pulling the codes? There are a handful of other things that can cause a limp other than oil temps and HPFP. 30FE and 30FF are ones that happened to every one of the 4 local 335s their first times at the track; simply due to the heat causing the rear wastegate sticking. Also VANOS codes pop up upon high heat as well. What were your oil temps getting to? Was everything going normal, then suddenly goes into limp? The reason I ask is because boost will taper down significantly before limp sets in. So you should've been able to realize that is happening then take a cool down lap or something.

If your street setup (440/500 HP/TQ) utilizes meth injection and keeps temps ~ 265, why the need to reduce power back to stock levels? From what I remember you have a Procede right? To go back down to 300 HP, are you going to run the methanol map (4) at something like 8psi in order to try get to your desired 250 track temp level? At 8psi, the meth wouldn't give you any extra power but perhaps it could keep oil temps down and prevent limp.

If your street setup (440/500 HP/TQ) utilizes meth injection and keeps temps ~ 265, why the need to reduce power back to stock levels? From what I remember you have a Procede right? To go back down to 300 HP, are you going to run the methanol map (4) at something like 8psi? At that level, the meth wouldn't give you any extra power but perhaps it could keep oil temps down and prevent limp.

No, I run a custom map for track duty; 12psi with meth. That keeps temps at 265. Same 12psi map without meth = 280* oil temps.

I don't even want to know what temps 400hp for 10 hard minutes would result in, haha

I could probably do a single hot lap at 14-15psi; but that's not what I was going for. This next year at the NASA and RL events; I'll be doing more of the single time attack laps...so boost/power will likely go up.

No, I run a custom map for track duty; 12psi with meth. That keeps temps at 265. Same custom map with 12psi = 280* oil temps.

I don't even want to know what temps 400hp would result in, haha

I could probably do a single hot lap at 14-15psi; but that's not what I was going for. This next year at the NASA and RL events; I'll be doing more of the single time attack laps...so boost/power will likely go up.

Interesting. I'm pushing ~ 425/475 RWHP/TQ to the wheels (17-18psi) with the Procede/PWM Meth system and did a hard 6 lap set around Big Willow after a few warm up laps. Oil temp gauge hit 250 and stayed right there through all 6 laps (so car was on the track for ~ 20 min straight, being pushed hard for about 10 min). The brakes quit on me otherwise I could have kept going...not sure for how long though but it seemed like the engine wasn't getting any hotter. I have zero cooling mods except meth. Willow is at 2,700 ft elevation and was fairly cool that day, so perhaps that also helped keep oil temps cool.

MFlowT5 tracks his car quite a bit at over 400+ wheel HP and meth and I don't remember him experiencing cooling issues. Maybe he can chime in.

Interesting. I'm pushing ~ 425/475 RWHP/TQ to the wheels (17-18psi) with the Procede/PWM Meth system and did a hard 6 lap set around Big Willow after a few warm up laps. Oil temp gauge hit 250 and stayed right there through all 6 laps (so car was on the track for ~ 20 min straight, being pushed hard for about 10 min). The brakes quit on me otherwise I could have kept going...not sure for how long though but it seemed like the engine wasn't getting any hotter. I have zero cooling mods except meth. Willow is at 2,700 ft elevation and was fairly cool that day, so perhaps that also helped keep oil temps cool.

MFlowT5 tracks his car quite a bit at over 400+ wheel HP and meth and I don't remember him experiencing cooling issues. Maybe he can chime in.

Hmm, what meth/water ratio? I'm at 75/25 for track and almost 100% meth for street. My thought process for this is to run a bit less boost and more ignition advance as opposed to more water (a little bit more cooling) and less timing.

Another thing that makes a large difference is the design of the track; more straights vs. twisties. For example, the two popular tracks around me are BIR (4 long straights, one of them being 1.1 miles long, the two 1/4 mile long, etc. and Road America also has many very long straights; and there is absolutely no area for the engine to cool on these tracks.

RA is known for being extremely hard on engines...and BIR as well. No question that that is attributing to the higher heat I'm experiencing. In any case, 265 or even 275 is not concerning; but anything above that is a bit uncomfortable.